A massive environmental cleanup of the polluted MichCon property in Ann Arbor is set to take place between August and October pending state approval.

Nearly 50 people packed into Cobblestone Farm Tuesday night to hear Michigan Department of Environmental Quality official discuss the plans submitted by DTE Energy.

MichCon has been a subsidiary of DTE since 2001. It ran a manufactured gas plant along the south bank of the Huron River decades ago and left the site polluted — a problem DTE inherited and is now working cooperatively with the DEQ to address.

"We're focused right now in 2012 on remediating any impacts related to the near-shore sediments and the near-shore soils, and then we're also looking at eliminating any of the hot spots that are still at the upland portion of the site," said Shayne Wiesemann, senior environmental engineer for DTE.

The site where the cleanup is expected to happen this year is nestled between the Argo Dam and the Broadway bridges near the Amtrak train station.

There appears to be strong public support for cleaning up the property, which city officials hope to turn into a riverfront park eventually.

"The remediation along the riverfront encompasses about 1,000 linear feet of shoreline," Wiesemann said. "We're looking at excavating around 22,500 cubic yards of impacted soil and sediment."

A handful of DEQ officials were in attendance for Tuesday's forum, including Ray Spaulding of the Remediation Division, James Sallee of the Water Resources Division, and Frank Ruswick, deputy director for the DEQ's Office of the Great Lakes.

DEQ District Supervisor Mitch Adelman gave a summary of the cleanup plan as well as a report on the property's background.

"There are some risks to human health and the environment from either the sediments or soils and that leads us to the plan that we've got in front of us," he said, describing some of the contaminants as "very viscous, dense, thick, black, smelly things."

He showed a photograph of the site believed to be taken around 1936 when large gas holders and oil tanks still stood near the river.

"This is but one of many former manufactured gas plant sites that are in the state of Michigan," Adelman said. "These are one of our legacies we all get to deal with."

Adelman said the DEQ is going to be closely reviewing the plans, but he doesn't anticipate any problems with DTE's ability to complete the remediation work in a safe manner.

"Our initial review is that this is a really good next step toward environmental remediation and bringing the facility to closure," he said, noting that additional remediation will be needed after this year's cleanup to be able to give the entire property a clean bill of health.

A history of pollution

According to information provided by the DEQ, MichCon and its predecessors operated a manufactured gas plant at the site from about 1900 until the late 1940s.

Consumer gas was produced on the site using a process that mixed coal and petroleum. During the manufacturing process, coal tar and other impurities were removed. Some of the industrial waste byproducts still contaminate the area today.

In the late 1950s, the plant was decommissioned and the site was converted into a MichCon service center by the early 1960s. Those operations were discontinued in 2008 and the main service center building was demolished between late 2009 and early 2010.

Adelman said the site has been on the DEQ's radar for years, with preliminary investigations into groundwater discharging into the Huron River dating back to 1985.

In 1993, a hole was found in a 12,000-gallon unleaded gasoline underground storage tank. During the course of the repair, about 3 inches of gasoline was discovered on top of the water table at a depth of four feet below grade. In addition to 113 gallons of "free product" being recovered, a site-wide investigation was conducted in 1996.

According to the DEQ, MichCon has spent $2.6 million performing site investigation and cleanup of 7,500 tons of soil and 1.3 million gallons of groundwater.

Over the years, MichCon has conducted a number of other investigations and interim environmental cleanup activities — with a focus on groundwater, soils and potential concentrated waste where gas manufacturing historically took place.

More recently, the focus has been on sediments in the main river channel between Argo Dam and the Broadway bridges.

In 1998, 1,680 cubic yards of impacted soil were excavated from the western part of the property, Adelman said.

That was followed by installation and operation of a groundwater treatment system from 2000 to 2005. Another 4,340 cubic yards of impacted soil were removed from the eastern part of the property in 2006, followed by removal of a storm sewer outfall in 2011.

Investigations have shown contaminants related to the former plant are present in sediments — but not in river water — at levels that may pose an unacceptable risk to human health and the environment, according to the DEQ.

Polycyclic aromatic hydrocarbons, which can cause health problems such as cancer, have been found in sediment at upstream locations and next to the MichCon site. According to the DEQ, the levels peak at near-shore areas in the vicinity of the former plant where a sheen is observed when the sediment is disturbed.

That's generally limited to within 15 feet of the south river bank, extending about 850 feet along the shoreline adjacent to the MichCon site, according to the DEQ.

Cleaning up the riverfront

DTE's plan is to dredge contaminated sediments from the main channel of the Huron River between Argo Dam and the Broadway bridges and also remove contaminated soils along the river banks to achieve an unrestricted residential cleanup standard. That means, for instance, the area being cleaned up will be considered safe to use as a public park.

Clean soil and rip-rap backfill will be placed in the river and the shoreline will be restored with new trees and other vegetation, according to the proposed plan.

After this year's cleanup, the DEQ is expecting DTE Energy to come forward with a proposal for final remediation of the remainder of the site within the next few years.

Wiesemann said the contaminants being removed this year are mainly polycyclic aromatic hydrocarbons, but there also are other elements such as chromium and lead.

Asked what the long-term plan is for the property and whether it could become a riverfront park, Wiesemann said DTE's focus is on this year's cleanup for now.

"In the terms of the whole property, we're waiting until we figure out what the final end use of the property is going to be so we can determine what the appropriate level of remediation is for that portion of the site," he said. "There's an understanding that there's a lot of potential for redevelopment of the site, but we're 100 percent focused on the remediation project.

"That being said, our leadership has a vision that this site is going to be one of an economic catalyst and will be used by the public for enjoyment."

Ann Arbor resident Stephen Kilijanczyk, who lives near Summit Street and Fourth Avenue across from Wheeler Park, voiced support for moving forward with the cleanup. An avid kayaker and paddle-boarder, he said he's looking forward to seeing a public use for the site.

"I see how it can be a major improvement to the area, especially for the fact that we've got that new waterway in for the kayaks," he said. "I feel it's crazy how they haven't developed this place. It's amazing. It's like a diamond in the rough — the whole riverfront.

"Ann Arbor has a riverfront and we're not using it."

City Council Members Stephen Kunselman, D-3rd Ward, and Jane Lumm, an Independent from the 2nd Ward, both attended the forum, as did a number of city staff members.

"I do hope that this property eventually becomes a city park. I think it will make a great addition to the Huron River greenway, which I think is really important," Kunselman said.

Commenting on the fact that the property is in a floodplain, Kunselman said it's probably not the best site to construct buildings, but he's not ruling out the possibility of a new train station, which is one idea some people have kicked around.

"I'm not as inclined to say 'no train station' there," he said. "I think that still remains to be seen, and to be honest, I think that's something the feds are going to have more of a decision than the local government, so I'll kind of let that one take its course."

Donald Gray, professor emeritus of civil and environmental engineering at the University of Michigan, chatted about the project with Russ Miller before the start of the forum.

They've both been closely following the debate over whether to remove Argo Dam, which has died down in the last year or two. Gray was concerned removing the dam would redirect the river through the polluted MichCon site, because that's its natural course.

"I'm delighted to see this happening," Gray said of the cleanup.

"I'm glad to see it moving forward and I'm hoping we can have at least a strip of it that can be park, because it really kind of completes the trail," Miller added. "We have this huge green swath through the city on either side of the river, so this is one of the last pieces of it."

Responding to a resident who asked how far downstream the MichCon contamination extends, Wiesemann said DTE Energy has done limited sediment sampling past the Broadway bridges and the results haven't been a cause for concern.

He said most of the contamination is located in front of the former plant site, but there could be some downstream impacts and that will have to be looked at in the future.

Ann Arbor resident Rita Mitchell asked about the restoration of plants along the riverbank. Wiesemann said DTE has been working with the city and the Huron River Watershed Council to come up with a nice riparian habitat that will include native grasses, shrubs and trees.

A DEQ official said Tuesday night there are dozens of former manufactured gas plant sites just like the one in Ann Arbor that are scattered across the state.

Ryan J. Stanton covers government and politics for AnnArbor.com. Reach him at ryanstanton@annarbor.com or 734-623-2529. You also can follow him on Twitter or subscribe to AnnArbor.com's email newsletters.